diff -u b/core/includes/file.inc b/core/includes/file.inc
--- b/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -205,8 +205,7 @@
  *   A string containing a URL that may be used to access the file.
  *   If the provided string already contains a preceding 'http', 'https', or
  *   '/', nothing is done and the same string is returned. If a stream wrapper
- *   could not be found to generate an external URL or a file doesn't have an
- *   external URL, then FALSE is returned.
+ *   could not be found to generate an external URL, then FALSE is returned.
  *
  * @see https://www.drupal.org/node/515192
  * @see file_url_transform_relative()
@@ -214,57 +213,58 @@
 function file_create_url($uri) {
   // Allow the URI to be altered, e.g. to serve a file from a CDN or static
   // file server.
-  try {
-    \Drupal::moduleHandler()->alter('file_url', $uri);
+  \Drupal::moduleHandler()->alter('file_url', $uri);
 
-    $scheme = StreamWrapperManager::getScheme($uri);
+  $scheme = StreamWrapperManager::getScheme($uri);
 
-    if (!$scheme) {
-      // Allow for:
-      // - root-relative URIs (e.g. /foo.jpg in http://example.com/foo.jpg)
-      // - protocol-relative URIs (e.g. //bar.jpg, which is expanded to
-      //   http://example.com/bar.jpg by the browser when viewing a page over
-      //   HTTP and to https://example.com/bar.jpg when viewing a HTTPS page)
-      // Both types of relative URIs are characterized by a leading slash, hence
-      // we can use a single check.
-      if (mb_substr($uri, 0, 1) == '/') {
-        return $uri;
+  if (!$scheme) {
+    // Allow for:
+    // - root-relative URIs (e.g. /foo.jpg in http://example.com/foo.jpg)
+    // - protocol-relative URIs (e.g. //bar.jpg, which is expanded to
+    //   http://example.com/bar.jpg by the browser when viewing a page over
+    //   HTTP and to https://example.com/bar.jpg when viewing a HTTPS page)
+    // Both types of relative URIs are characterized by a leading slash, hence
+    // we can use a single check.
+    if (mb_substr($uri, 0, 1) == '/') {
+      return $uri;
+    }
+    else {
+      // If this is not a properly formatted stream, then it is a shipped file.
+      // Therefore, return the urlencoded URI with the base URL prepended.
+      $options = UrlHelper::parse($uri);
+      $path = $GLOBALS['base_url'] . '/' . UrlHelper::encodePath($options['path']);
+      // Append the query.
+      if ($options['query']) {
+        $path .= '?' . UrlHelper::buildQuery($options['query']);
       }
-      else {
-        // If this is not a properly formatted stream, then it is a shipped file.
-        // Therefore, return the urlencoded URI with the base URL prepended.
-        $options = UrlHelper::parse($uri);
-        $path = $GLOBALS['base_url'] . '/' . UrlHelper::encodePath($options['path']);
-        // Append the query.
-        if ($options['query']) {
-          $path .= '?' . UrlHelper::buildQuery($options['query']);
-        }
-
-        // Append fragment.
-        if ($options['fragment']) {
-          $path .= '#' . $options['fragment'];
-        }
 
-        return $path;
+      // Append fragment.
+      if ($options['fragment']) {
+        $path .= '#' . $options['fragment'];
       }
+
+      return $path;
     }
-    elseif ($scheme == 'http' || $scheme == 'https' || $scheme == 'data') {
-      // Check for HTTP and data URI-encoded URLs so that we don't have to
-      // implement getExternalUrl() for the HTTP and data schemes.
-      return $uri;
-    }
-    else {
-      // Attempt to return an external URL using the appropriate wrapper.
-      /* @var \Drupal\Core\StreamWrapper\StreamWrapperInterface $wrapper */
-      if ($wrapper = \Drupal::service('stream_wrapper_manager')->getViaUri($uri)) {
+  }
+  elseif ($scheme == 'http' || $scheme == 'https' || $scheme == 'data') {
+    // Check for HTTP and data URI-encoded URLs so that we don't have to
+    // implement getExternalUrl() for the HTTP and data schemes.
+    return $uri;
+  }
+  else {
+    // Attempt to return an external URL using the appropriate wrapper.
+    if ($wrapper = \Drupal::service('stream_wrapper_manager')->getViaUri($uri)) {
+      try {
         return $wrapper->getExternalUrl();
       }
+      catch (\Exception $e) {
+      }
+      return FALSE;
+    }
+    else {
+      return FALSE;
     }
   }
-  catch (\Exception $e) {
-  }
-
-  return FALSE;
 }
 
 /**
reverted:
--- b/core/lib/Drupal/Core/StreamWrapper/StreamWrapperInterface.php
+++ a/core/lib/Drupal/Core/StreamWrapper/StreamWrapperInterface.php
@@ -145,9 +145,8 @@
    * "youtube://xIpLd0WQKCY" might be
    * "http://www.youtube.com/watch?v=xIpLd0WQKCY".
    *
+   * @return string
+   *   Returns a string containing a web accessible URL for the resource.
-   * @return string|false
-   *   Returns a string containing a web accessible URL for the resource or
-   *   FALSE if a stream doesn't/cannot provide the URL.
    */
   public function getExternalUrl();
 
reverted:
--- b/core/modules/locale/src/StreamWrapper/TranslationsStream.php
+++ a/core/modules/locale/src/StreamWrapper/TranslationsStream.php
@@ -41,11 +41,12 @@
   }
 
   /**
+   * Implements Drupal\Core\StreamWrapper\StreamWrapperInterface::getExternalUrl().
+   * @throws \LogicException
+   *   PO files URL should not be public.
-   * {@inheritdoc}
    */
   public function getExternalUrl() {
+    throw new \LogicException('PO files URL should not be public.');
-    // PO files URL should not be public.
-    return FALSE;
   }
 
 }